IR related article links

I have collected some articles to build the knowledge of Information retrieval. I will keep adding the links to this post

1. Simple Search boolean retrieval : This article explains the theroy of boolean retrieval along with a small example.
2. Simple Search phrases : This article deals with the phrase search
3. Hadoop Mapreduce Examples : This post gives a solution to various map reduce problems as listed in Mannings publication "Hadoop in Action"